1. Field of the Invention
This invention relates to a pressure-sensitive skin adhesive for fastening flat, flexible substrates such as adhesives, wound plasters, and adhesive plasters or transdermal drugs to the skin. A pressure-sensitive adhesive is one that is permanently flexible as a dried film and that removably fastens a solid substrate that is pressed on. However, the dried adhesive film does not have to be anhydrous. The desired adhesiveness frequently occurs only when the adhesive film is dried out in the air and does not dry further by itself, but is in moisture equilibrium with the skin.
This invention also relates to a solution of the pressure-sensitive skin adhesive and its use for application to flexible, flat substrates. Finally, the invention also relates to wound plasters and adhesive plasters and transdermal drugs.
2. Background of the Prior Art
A fastening agent for medical purposes consisting of an alcohol solution of polymers containing carboxyl groups, or interpolymers of polymerizable ethylene compounds and plasticizing or resinous substances, and optionally pigments and fillers is already known from DE-PS 855 615.
A suitable copolymer, for example, is made up of 40% methacrylic acid and 60% methyl methacrylate. Since by itself it is hard and not adhesive, 9 parts of polyvinyl methyl ether and 3 parts of glycerin are used as plasticizer with 2 parts of the copolymer. The mixture is applied to the skin from alcohol solution and is used to fasten bandages. The polymer film is water-resistant. However, since the copolymer is water-soluble in the form of its alkali metal salt, it can be washed off of the skin with a weakly alkaline soap solution.
EP-B 35 399 describes an adhesive polyacrylate for application to the skin that has a K value of 90 to 110 and is made up of 16-62% n-butyl acrylate, 34-80% 2-ethylhexyl acrylate, and 4-10% acrylic acid. Because of the high proportion of higher acrylic esters, the copolymer is soft and adhesive and does not require the addition of a plasticizer. This adhesive is processed from organic solution, for example in acetone, to make a pressure-sensitive adhesive film for a self-adhesive plaster or adhesive tape.
A pressure-sensitive skin adhesive whose adhesive strength on the skin depends strongly on the moisture content is disclosed by WO 84/03837. It contains a copolymer of a hydrophobic monomer from the group of alkyl esters of acrylic acid with 4 to 14 carbon atoms in the alkyl group, with 0.5-30% of a hydrophilic monomer from the group consisting of acrylic and/or methacrylic acid, acrylamide, and/or methacrylamide, itaconic acid, and vinylpyrrolidone, and 5-30% of another hydrophilic monomer such as polyethylene glycol acrylate or methacrylate.
Chem. Abstr. 99, 128 355 refers to JP-A 83/103 317, concerning an adhesive film for transdermal drugs that contains as the adhesive resin a copolymer of 0.1-15% of the ammonium salt of acrylic and/or methacrylic acid along with other monomers. The adhesive resin after adding water is applied to a carrier film in the form of a hydrosol. Ammonia escapes on drying, so that the acidic copolymer remains behind in the adhesive film.
Chem. Abstr. 98, 185 617 (JP-A 83/15 911) likewise describes an adhesive film for transdermal drugs. As adhesive resin it contains a crosslinked, partly neutralized polymer of an unsaturated carboxylic acid, with glycerin and gelatin as plasticizers. Because of the crosslinking the adhesive resin is insoluble.
In accordance with Chem. Abstr. 97, 188 313 (JP-A 82/134 415), copolymers of butyl acrylate and ammonium acrylate that are plasticized with polyoxypropylenesorbitan and crosslinked by polyepoxide resins are used for the same purpose.